The U.S. is trying to develop a strategy to deal with ISIS, an Islamist extremist group that has seized large chunks of territory in Iraq and Syria and gained worldwide attention for killing American journalist James Foley.

During a taping of WMUR's "CloseUP," Scott Brown said the fight needs to be taken to ISIS. He said he would file a bill stripping Americans of their passports if they are deemed to be working with the terrorist group.

"We can put our heads in the sand and call them the JV, or we can get involved and go and do something," Brown said. "I, quite frankly, don't want to see them plant a flag in the White House, and I also don't want to see them continue to murder our citizens."

Former Sen. Bob Smith said he believes it's a fight the U.S. can't win overseas.

"The thing, though, is when the president says, 'I don't have a strategy,' I shudder when I hear that," Smith said. "Because it's Vietnam all over again -- no exit strategy. Why are we going in?"

Candidate Jim Rubens falls somewhere in between.

"We don't seem to have any plan over there," Rubens said. "Instead, what we need is far better on-the-ground intelligence, and if it's disclosed that individuals or groups have plans or plots that can harm Americans, we can use surgical techniques."

As far as the primary race goes, polls indicate Brown is the frontrunner, but Smith and Rubens insisted that they draw clearer distinctions against incumbent U.S. Sen. Jeanne Shaheen.

"I believe that the way to win against Jeanne Shaheen is to show the difference between what she represents and what I represent, and I'm the only candidate that can do that," Smith said.

"I'm down there like a volunteer fireman to lift this country up and to improve people's lives and not to be owned and operated by special interests," Rubens said. "And this is a difference, and I'm making the case to the people of New Hampshire."

"The people of New Hampshire want a true, independent leader," Brown said. "Bob and Jim are great guys, and if they win, I'll be the first one to support them. But if I win, I need them to do the same thing, because a united Republican party is Sen. Shaheen's worst nightmare."

Hear more from the three candidates on "CloseUP" at 10 a.m. Sunday on WMUR-Channel 9.

The three will also be on the debate stage Thursday as part of WMUR's Granite State Debates series. The hour-long debate starts at 7 p.m. and can be seen live on Channel 9 and WMUR.com.